This invention relates to a process for reducing the level of compounds of certain metals from hydrocarbon liquids by contacting the hydrocarbon with particulate active carbon which has been pretreated with a highly acidic oxidizing medium.
Removal of metal components from hydrocarbons is desirable under certain circumstances. In the refining of petroleum, various oils which have become contaminated or fail to meet one or more specifications, typically are collected and recycled as charge stock for refining processes, particularly those employing catalysts comprising Group VIII metals such as nickel, cobalt and platinum. Accordingly, it is highly desirable to remove lead compounds from the oil. Further, governmental regulations now require the marketing of gasolines having at most 0.05 grams of lead per gallon, in order to prevent poisoning of noble metal-containing catalytic mufflers installed on internal combustion engines. As a result, some gasolines are now being commercialized with organo manganese antiknock compounds which apparently do not seriously impare the noble metal-containing mufflers. Accordingly, a process to selectively remove lead compounds from gasoline with little if any reduction in organo manganese compounds is of considerable interest.
Although the nonleaded gasolines may be produced at the refineries with sufficiently low lead level to meet the legal requirement, occasionally they will absorb small but significant amounts of lead compounds from storage, or transport of fuels in lead contaminated tanks and pipelines to exceed this limit.
In addition to lead, the presence of other metals such as copper, iron, nickel or chromium in hydrocarbon fuels tends to promote deposits and corrosion and to accelerate maintenance problems in the furnaces, turbines and related combustion equipment. Accordingly, a process to reduce such contaminants is highly desirable.
A variety of methods have been proposed for the removal of e.g. lead alkyl compounds from light hydrocarbons. These include e.g. chemical reaction with bromine, stannic chloride, sulfur dioxide and nitrogen dioxide; adsorption on ion exchange resins, silica gel or activated clays; and thermal decomposition. Deficiencies in these procedures are presented e.g. in an article by Johnson et al in Hydrocarbon Chemistry, October 1975, page 119. Additionally, it has been proposed to remove lead alkyls by contacting with ferric or cupric chloride impregnated into activated carbon. It is known that the capacity of at least the ferric chloride-containing material is reduced by the presence of large amounts of catalytically cracked naphthas. The copper impregnated carbon requires the presence of water to minimize leaching of the copper into at least certain gasoline compositions.